1. Technical Field
Embodiments of the present invention are directed to a method and apparatus for mixing fluids, whereby the fluids are mixed due to the generation of turbulent flow.
2. Description of the Related Art
Biochips and biosensors are micro devices that allow various experiments and assays currently performed in a laboratory to be performed on a single small chip. Examples of biochips include microfluidic chips that are commonly used for gene assays or biochemical assays. With regard to microfluidic chips, a small amount of a sample is loaded into micro channels formed in a microfluidic chip so as to react with various chemical molecular sensors integrated in the microfluidic chip. Microfluidic chips are designed to perform isolation, synthesis, and quantification of a sample. Assays using biochips use effective mixing operations of various samples, such as operations for cell activation, enzyme reactions, and protein synthesis. However, in a micro-level system, fluids have a small Reynolds number and thus flow in a laminar flow pattern, and samples in microfluidic devices are mixed only by diffusion. Thus, a long time is required to effectively mix samples, thereby affecting the entire assay system.
Conventional techniques for effectively mixing micro samples can be classified into active mixing methods and passive mixing methods. Active fluid mixers used in active mixing methods use external energy, such as external pressure or an electric field, and actively control fluid flow. For example, magnetic beads or pneumatic devices may be used. However, when magnetic beads are used, additional devices for moving the magnetic beads, as well as additional processes of loading the magnetic beads into a chamber, are required, thus complicating the manufacturing process. When pneumatic devices are used, many switches need to be formed in the channels, which also complicates the manufacturing process.
On the other hand, passive mixing methods do not use additional energy but only use fluids flowing at a predetermined flow rate, and mixing performance is improved only by changing the structure of the channels. Although passive mixing methods have lower mixing performance than active mixing methods, passive mixing methods are inexpensive and useful for micro devices. For example, structures for passive mixing methods include stacked films having T-shaped or Y-shaped fluidic structures, or slanted recesses arranged in channels. However, these structures are complex and challenging to manufacture, and effective mixing does not occur.